The objectives of the Genetically Engineered Mouse (GEM) shared resource is to aid Cancer Center investigators with the design and execution of experiments to utilize animal models for the investigation of the progression of cancer and in the preclinical evaluation of therapies for the treatment of cancer. Although the use of animal models provides an invaluable source of reagents for preclinical testing and the investigation of regulatory mechanisms in vivo, in a physiologically regulated system, the use of animals is costly with respect to equipment, animal resources and technical expertise. GEM will serve as a resource for the execution and training in the use of all animal manipulations needed in the Cancer Center. The GEM shared resource will minimize the cost of utilizing animal models in the Cancer Center by consolidating animal expertise and associated equipment. This will ensure an efficient use of animal research at minimal cost. The GEM shared resource will serve Cancer Center investigatory by aiding in the following tasks. 1. Generate transgenic mice by the micro injection of DNA into the one celled mouse embryo. 2. Generate mutant mice by the manipulation of mouse Embryonic Stem Cells. 3. Preserve lines of mice by cryopreservation. 4 Assist investigators with the importation and exporting of lines of mice. The accomplishments of these tasks will allow the GEM Shared Resource to serve as a repository for all genetically engineered mouse models and techniques for Cancer Center investigators and will ensure efficient use of animal resources by Cancer Center investigators.